Adjustable load stabilizer frame for forklift truck and method

ABSTRACT

An adjustable frame for a load stabilizer mounted in vertically spaced and substantially superimposed relation over fork means on a forklift truck is disclosed. The frame includes a reciprocating extension means mounted to the forklift carriage and a reciprocating stabilizer carrying frame portion, preferably telescopically mounted with respect to the extension means. A locking sleeve formed to allow selective locking to both or one of the extension means and stabilizer frame is also provided for adjustment of the range heights through which the stabilizer may be positioned. A method, which can be performed by a single forklift operator, of adjusting the stabilizer by alternately utilizing the stabilizer driving means and the carriage on which the stabilizer is mounted to support the weight of the stabilizer is also disclosed.

United States Patent [1 1 Dutra, Jr.

[451 Nov. 20, 1973 ADJUSTABLE LOAD STABILIZER FRAME FOR FORKLIFT TRUCK AND METHOD [76] Inventor: Joseph G. Dutra, Jr., 4568 Thornton Ave., Fremont, Calif. 94536 [22] Filed: Aug. 28, 1972 [21] Appl. No.: 284,334

Primary Examiner-Gerald M. Forlenza Assistant Examiner-George F. Abraham Att0rneyManfred M. Warren et al.

[5 7 ABSTRACT An adjustable frame for a load stabilizer mounted in vertically spaced and substantially superimposed relation over fork means on a forklift truck is disclosed. The frame includes a reciprocating extension means mounted to the forklift carriage and a reciprocating stabilizer carrying frame portion, preferably telescopically mounted with respect to the extension means. A locking sleeve formed to allow selective locking to both or one of the extension means and stabilizer frame is also provided for adjustment of the range heights through which the stabilizer may be positioned. A method, which can be performed by a single forklift operator, of adjusting the stabilizer by alternately utilizing the stabilizer driving means and the carriage on which the stabilizer is mounted to support the weight of the stabilizer is also disclosed.

7 Claims, 4 Drawing Figures P TENTED nuv 20 I975 SHIFT 2 CF 2 ADJUSTABLE LOAD STABILIZER FOR FORKLIFT TRUCK AND METHOD BACKGROUND OF THE INVENTION The use of forklift trucks, lift trucks or hoist trucks is widespread in many branches of industry today. In certain applications it has been found to be very advantageous and often absolutely necessary to employ a forklift truck having a load stabilizer means mounted in vertically spaced substantially superimposed relation over the forks of the forklift truck. Such load stabilizers are sometimes referred to as box or load clamps and are also in widespread use. Usually the load stabilizer is mounted by means of a frame to the vertically movable carriage to which the forks of the forklift truck are attached. The load stabilizer is driven by stabilize r driving means, such as a hydraulic piston and cylinder, which operates independently of the driving cylinder for the carriage and forks.

A problem which has been commonly encountered in connection with the use of load stabilizers or box clamps has been that the size of the load which is carried on the forks can vary considerably. Thus, the box clamp should be able to clamp loads as small as about 3 7% feet high as well as loads as large as about 11 feet high. One approach to solving this problem is to employ a piston and cylinder drive for the stabilizer which has a relatively long displacement or stroke distance. This type of approach can be seen in U.S. Pat. No. 2,684,165, and is somewhat unsatisfactory in that it tends to increase the height of the forklift undesirably, makes the stabilizer unsuitable for use on relatively low loads, and generally limits the range of travel of the stabilizer to that of the piston. Similarly, more complicated load stabilizersare disclosed in U.S. Pat. Nos.

3,024,929 and 3,567,053, but they do not contemplate adjustment of the range of heights which the load stabilizer may be reciprocated over the fork means beyond the travel of the piston in the driving cylinder.

Another approach to the problem of increasing the capability of the load' stabilizer to handle loads which vary substantially in height has been to employ telescoped or nested cylinders to drive the stabilizer unit. Typical of this technique are the devices shown in U.S. Pat. Nos. 2,807,382 and 3,272,364. While telescoped stabilizer driving cylinders will afford an improvement in the range of heights through which the load stabilizer may be adjusted, this type of hydraulic equipment is inherently substantially more expensive in terms of initial investment and upkeep than the standard single piston and cylinder.

Still another approach is illustrated in U.S. Pat. No. 3,133,655, and it employs a loadstabilizer frame which is adjustable so that a single piston and cylinder can be employed with the adjustable frame to achieve adjustment of the load stabilizer. Adjustable frames of this type are manually operable and typically require three or four people to support the stabilizer and raise or lower the same while a pin or bolt is used to secure the stabilizer at a selected height with respect to the stabilizer frame and the driving piston and cylinder. While this approach avoids the cost of telescoped stabilizer driving cylinders, it does require a plurality of people to adjust the stabilizer height. The need for others to support and raise and lower the load stabilizer becomes particularly acute when sophisticated and usually heavy load stabilizing clamps are employed.

Accordingly, it is an object of the present invention to provide a load stabilizer for a forklift truck and method of adjusting the same which canzbe easily and quickly adjusted by a single operator to accommodate clamping of loads having a wide range of vertical heights.

Another object of the present invention is to provide a load stabilizer which is adjustable through a wide range of heights and yet is inexpensive and can be economically added to a forklift truck.

Still another object of the present invention is to provide a load stabilizer which is adjustable and a method of adjusting the same which can be operated by relatively unskilled personnel, is durable and inexpensive to operate, andenabl es adjustment without relying on the strength of the operator.

The adjustable load stabilizer and method of the present invention has other features and objects of advantage which will become apparent and are set forth in more detail hereinbelow and in the accompanying drawings.

SUMMARY OF THE INVENTION The adjustable load stabilizer of the present invention is comprised, briefly, of a reciprocating extension means mounted to the carriage on which the fork means of the forklift truck is carried, a stabilizer frame portion mounted to the extension means for vertical reciprocation with respect thereto and having the load stabilizer secured to an'upper end thereof, and locking means secured tostabilizer driving means for movement therewith and, positioned adjacent the extension means and frame portion, the locking means being formed for selective reciprocation with respect to the extension means and .frame portion and forselective securement to one or both of the. extension means and frame portion. The extension means and frame portion are preferably relatively telescoped and further mounted in telescoped relation to a guide means mounted on the carriage. The locking means is preferably formed asa sleeve surrounding the extension means and frame portion and a plurality of pins which may be inserted into channels or openings in the extension means and frame portion.

The method of the present invention is comprised, briefly, of supporting the weight of the stabilizer means alternatively on guide means fixed to the carriage .through the extension element and directly on the stabilizer driving means while the sleeve through which the driving means is connected to the frame and the stabilizer is selectively unlocked from a first position on the stabilizer frame and locked to an adjusted position on the frame;

BRIEF'DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of a forklift truck having a load stabilizer constructed in accordancewith the-present invention mounted thereon.

FIG. 2 is a front, elevational view of the load stabilizer of FIG. I shown in extended position.

FIG. 3 is an enlarged, fragmentary, cross-sectional view taken along the plane of line 33 of FIG. 2.

FIG. 4 is an-enlarged, fragmentary, cross-sectional view taken along the plane of line 4-4 in FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT The adjustable load stabilizer of the present invention can be mounted to almost any forklift truck. As may be seen in FIG. 1, a forklift truck, generally designated 21, will usually be provided with an upright lift frame 22 to which a movable carriage 23 is mounted for vertical reciprocation. Carriage 23.is further provided with fork means 24, usually a pair of fork elements, for support and lifting of loads. Lift frame 22 is usually formed as a pair of opposed C-shaped channels and carriage 23 includes rolling elements mounted in the channels of lift frame 22 to enable guided reciprocation of the carriage within the frame. Additionally, carriage driving means (not shown), such as a hydraulic cylinder and piston, are provided to enable reciprocation of carriage 23 within lift frame 22. Still further,

lift frame 22 is normally pivotally mounted for rotation about a horizontal axis at the base of the lift frame to enable tilting of frame 22 for control of the load being lifted. Such tilting can be accomplished by means of a hydraulic cylinder 26 and associated linkage 27 between the cylinder, which is mounted to the body of the truck, and lift frame 22.

As best may be seen in FIGS. 1 and 2, load stabilizer means, generally designated 31, is mounted on a stabilizer frame means 30 in vertically spaced and substantially superimposed relation to fork means 24 for vertical reciprocation thereover. Stabilizer frame means 30 includes an upper movable frame portion 32 which is connected, in a manner which will be more fully set forth hereinafter, to a lower frame guiding structure 47. Guiding structure 47 is in turn fastened by cross members 34 and 36 and by fasteners 25 to carriage 23 so that the stabilizer means will be vertically reciprocated upon reciprocation of carriage 23 and fork means 24. Additionally, in order to provide for clamping action by the stabilizer, stabilizer driving means, generally designated 33 and best seen in FIG. 2, is connected to stabilizer means 31 to raise and lower the stabilizer through a range of heights with respect to fork means 24. Thus, cross members 34 and 36, which connect guide elements 47 to carriage 23 also have hydraulic cylinder 37 and piston 38 mounted thereto bylinkage 39. Mounted on the upper end of piston 38 is a cross bar member 41 which in turn is secured to frame portion 32 in a manner more fully set forth hereinafter in order that the driving force of the piston and cylinder can be used to raise and lower stabilizer means 31 with respect to carriage 23. Additionally, a protective cover 35 surrounds cylinder 37 to protect the same against damage by loads carried on forks 24.

In use, the carriage will be lowered until forks 24 can be placed under the load, usually supported on a pallet. Stabilizer means or box clamp 31 will then be lowered by the piston and cylinder comprising the driving means 33 until box clamp engaging element 42 contacts the upper surface of the load. Although various box clamp or stabilizer constructions are suitable for use with the present invention, the stabilizer shown includes load engaging element 42 whichfis resiliently downwardly biased by spring means 43. Additionally, side clamps 44 are actuated to pivot inwardly as load engaging element 42 is upwardly displaced. When the stabilizer is clamped on the load, the lift cylinder may then be employed to raise carriage 23 and accordingly lift the forks and box clamp simultaneously and without releasing the clamping force on the load. The general structure thus far described, with the exception of the specific box clamp structure, may be found in prior forklift truck apparatus and has the disadvantages previously noted. I Iv In order to provide a load stabilizer in which the range of heights over the fork means can be quickly and easily adjusted by a single operator, the frame portion 32 of the load stabilizer is mounted for vertical reciprocation with respect to extension means 46, which in turn is mounted for vertical reciprocation to guide means 47. Additionally, the adjustable frame includes locking means, generally designated 48, which is mounted on the ends of cross bar 41 for movement of the locking means with driving means 33. Looking means 48 is positioned adjacent, and preferably substantially surrounds, extension means 46 and frame portion 32, and the locking means is formed for reciprocation with respect to the extension means and frame portion. Still further, locking means 48 is formed for securement to one or both of extension means 46 and frame portion 32 for selective reciprocation of one or both of these elements by the stabilizer driving means to effect adjustment of the range of heights through which stabilizer 31 may be reciprocated.

The operation of the adjustable load stabilizer frame of the present invention can be described in more detail by reference to FIGS. 2, 3 and 4. In order to facilitate selective locking of sleeve 48 to frame portion 32, the frame portion is preferably formed with a plurality of vertically spaced, horizontally extensing channels 50-54, and these channels or bores are preferably periodically spaced at predetermined intervals over the heighth of frame members 32, as indicated generally by bores 57. As also will be seen in FIG. 3, frame portion 32 is preferably telescoped inside a tubular extension means or member 46 which is also formed with a channel or bore 61 in the upper end thereof, Extension element 46 is mounted in telescoped relation to tubular guide means or element 47 and is gravity biased and supported with respect to the same by a shoulder or stop means 62 fixedly secured to extension member 46.

Mounted for sliding vertical reciprocation with respect to frame portion 32 and tubular extension member 46, is locking means 48 which is comprised of a sleeve 63 mounted on the end of cross bar 41 and formed with a pair of vertically spaced, horizontally extending channels or bores 66 and 67 through which locking pins 68 and 69 may be positioned upon registration of corresponding channels in frame portion 32 and extension member 46.

In operation, the apparatus of the present invention allows adjustment of the range of heights through which the box clamp can be reciprocated by a single operator alternatively supporting the weight of the box clamp on the piston and cylinder of the driving means and on the carriage by means of the adjustable frame. First, driving means 33 may be used to vertically position the stabilizer as shown in FIG. 3. Pin-or bolt 69 may then be removed from sleeve 63, extension member 46 and frame portion 32. Thus, the sleeve is secured to frame portion 32 by pin 68 but is now released from the tubular extension element. Driving means 33 can be used to vertically displace cross bar 41, sleeve 63 and frame member 32. Frame member 32 will reciprocate inside tubular sleeve 46 which is supported by stop means 62 to guide element 47. Thus, the stabilizer means can be used to displace frame portion 32 until bore or channel 50 aligns with bore or channel 61 at the upper end of extension member 46. When channels 61 and 50 are aligned, pin 69 can be placed through the extension member and frame, but not through the sleeve which is now vertically reciprocated, to secure frame 32 to extension member 46 and to guide element 47 through shoulder 62 for support of the weight of the stabilizer means by the guide tube 47. Once the weight of the stabilizer is supported through the frame to the carriage of the forklift truck, pin 68 may be removed from sleeve 63 to release the sleeve from the frame portion while maintaining the frame portion secured and supported through extension member 46 to the guide element 47. The stabilizer means may now be used to vertically displace the sleeve with respect to the frame portion.

If the range of heights is to be adjusted upwardly, sleeve 63 would be reciprocated downwardly with respect to frame portion 32 until channel 66 in the sleeve is in alignment with a channel or bore below channel 53, e.g., channel 52. If the stabilizer is to be lowered, sleeve 63 would be reciprocated by driving means 33 until channel 66 is aligned with a channel above channel 53, e.g., channel 54 in frame portion 32. In either of these selected positions pin 68 may again be reinserted so as to lock the sleeve means to the frame at the adjusted position, either bore 54 or bore 52. Once the sleeve is relocked to frame 32, the weight of the stabilizer may be supported by the piston and cylinder of driving means 33, and pin 69 may be removed from extension 46 and frame 32. The driving means can then be used to displace the sleeve and frame downwardly until channel 67 in the sleeve again aligns with channel 61 in extension element 46, at which point pin 69 can be reinserted to lock the extension means to the sleeve means at the new position on frame portion 32. It should be noted that, since the extension means is only gravity biased to rest on guide member 47, extension means 46 can be upwardly displaced to be pinned to sleeve 63 instead of lowering the sleeve and stabilizer.

An operator may, therefore, easily adjust the stabilizer of the present invention by pulling the lower pin on the sleeve, raising the stabilizer by the driving means connected to the frame by the upper pin, locking the stabilizer to the carriage by reinsening the lower pin just through the extension means and the frame, releasing the sleeve from the frame, reciprocating the sleeve with respect to the frame to the adjusted position, pinning the sleeve to the frame at the adjusted position, releasing the extension means from the frame, and downwardly displacing the sleeve or upwardly reciprocating the extension means until the extension means may be resecured to the sleeve by means of the lower pin. Thus, an unassisted operator can achieve the adjustment simply by using the hydraulic system of the load stabilizer, the locking sleeve apparatus and extension element to effect the adjustment without having to manually support the weight of the stabilizer.

The importance of extension element 46 is particularly well illustrated in FIG. 2 wherein the tubular extension element on the right side of the stabilizer means is shown pinned to sleeve 63, and piston 38 is fully extended from cylinder 37. On the right side of the stabilizer, end 71 of frame portion 32 will be seen to be telescoped inside a substantial length of sleeve 46 and end 72 of sleeve 46 telescoped inside guide tube 47. If the extension member was not present, the end 71 would be displaced out of the tubular guide member 47, as shown on the left side of FIG. 2 (element 46 on the left side of FIG. 2 normally would be downwardly biased by gravity until stop member 62 rested on the top 73 of guide tube 47 once the lower pin is removed from channel 61). The extension element, therefore, allows a substantial increase in the range of heights through which the box clamp may be adjusted. It should be noted that it would be possible to have more than one telescoped extension element on each side of the stabilizer frame to further increase the range of heights through which the box clamp can be adjusted. Sleeve 63 would be formed for selective securement to each of the additional extension elements, and the extension elements would be formed for securement to the frame portion or another extension element.

Elimination of extension element 46 inmost instances is not desirable, although it is possible. Usually, the stabilizer driving means will have a displacement substantially equal to the guide tubes 47. Thus, unless the frame portion can extend down below the bottom 74 of guide tubes 47, adjustment of the sleeves with respect to the frame portion will merely cause the frame to be lifted out of the guide tubes. In certain limited sitnations, however, it may be possible to extend frame portion 32 below the lower ends 74 of the tubular guide elements. When such an approach is permissible, extension element 46 can be eliminated and a channel provided in the upper end of guide element 47 to enable pinning of the frame 32 to the guide element while sleeve 63, which would have only one channel therethrough, is vertically reciprocated during adjustment.

As best may be seen in FIG. 3, tubular extension means 46 is preferably provided with a second shoulder or stop ring 76 which is engaged by a shoulder or stop 77 on sleeve 63. This second stop has the advantage of insuring that the openings 67 in the sleeve will always line up with openings 61 in the extension member merely by allowing the sleeve to be downwardly displaced until shoulders 76 and 77 engage each other. Moreover, since the frame is pinned to sleeves 63 and the channels are spaced in the frame at a predetermined distance, channel 52 will automatically align with the channels in the sleeve and extension member as shoulders 76 and 77 come into engagement. As will be seen, however, it is also possible to eliminate ring 76 and achieve alignment or registration of the respective channels by engagement of shoulder 78, which acts as a stop means, with the upper end 79 of extension member 46.

I claim:

1. In a forklift truck having an upright lift frame, a movable carriage mounted to said frame for vertical reciprocation, said carriage further being provided with fork means for support of a load, load stabilizer means mounted in vertically spaced and substantially superimposed relation to said fork means for vertical reciprocation thereover, and stabilizer driving means connected to said stabilizer means to raise and lower said stabilizer means through a range of heights with respect to said fork means, the improvement comprising:

an adjustable load stabilizer frame mounting said stabilizer means on said carriage for selective adjustment of the range of heights above said fork means through which said stabilizer means can be raised and lowered, said stabilizer frame including:

1. a reciprocating extension means mounted on said carriage for reciprocation in a vertical'direction with respect to said fork means;

2. a stabilizer frame portion mounted on said extension means for vertical reciprocation with respect to said extension means and to said fork means, said stabilizer means being mounted on said frame portion; and

3. locking means secured to said stabilizer driving means for movement therewith, said locking means being positioned adjacent said extension means and said frame portion and formed for reciprocation with respect thereto and for selective securement to both said extension means and said frame portion, and said locking means being further formed for securement to one of said extension means and said frame portion for reciprocation of only the secured one thereof by said stabilizer driving means.

2. A forklift truck having an adjustable load stabilizer frame as defined in claim 1 wherein,

said carriage is formed with a vertically extending guide means; and

said extension means is mounted for reciprocation on said guide means, said guide means, extension means and frame portion being mounted in relatively telescoped relation.

3. A forklift truck having an adjustable load stabilizer frame as defined in claim 2 wherein,

said frame portion is formed with a plurality of vertically spaced horizontally extending channels therethrough; and

said locking means is formed as a sleeve substantially surrounding said extension means and said frame portion and formed with a plurality of vertically spaced horizontally extending channels, and one of said channels of said locking means is further alignable with a horizontally extending channel through an upper end of said extension means, at least a pair of said channels in said frame portion being postionable in relative registration with a pair of channels in said sleeve, and said channel in said extension means capable of being in registration with one of said channels in said sleeve and one of said channels in said frame portion, and said locking means further including at least a pair of pin elements removably mounted to extend into said registered channels in said sleeve, said extension means and said frame portion. 7

4. A forklift truck having an adjustable load stabilizer frame as defined in claim 2, and

stop means mounted on said extension means and formed to limit the downward reciprocation of said locking means with respect to said extension means and further formed to limit the downward reciprocation of said extension means with respect to said guide means; and wherein,

said locking means is formed for releasablesecurement to said frame portion at a first vertical position thereon, and said extension means is formed for releasable securement to said frame portion at a second vertical position thereon.

5. A forklift truck having an adjustable load stabilizer frame as defined in claim 1, wherein said carriage includes a pair of laterally spaced, vertically extending, tubular guide elements fixedly secured to said carriage for movement with said fork means;

said extension means is formed by a pair of tubular extension members telescopically mounted for vertical reciprocation in said guide elements;

said frame portion is formed by a pair of frame members telescopically mounted for vertical reciprocation in said pair of tubular extension members and said frame members have said stabilizer means secured to the upper ends thereof;

said stabilizer driving means is formed as a hydraulic piston and cylinder and pump means therefor, and one of said piston and cylinder is secured to said carriage and the remaining of said piston and cylinder is secured to a transverse cross-bar extending between said pairs of telescopically mounted members; and

said locking means includes, a pair of sleeves secured to opposite ends of said transverse cross-bar with each sleeve being mounted in sliding engagement around said telescopically mounted members, and locking pin means mounted on each of said sleeves and formed for selective releasable securement to said pair of tubular extension members and for selective releasable securement to said pair of frame members.

6. A method of adjusting the height of a load stabilizer means over a fork means mounted on a vertically reciprocal carriage on a forklift truck comprising:

vertically positioning said stabilizer means to a selected vertical height over said fork means by load stabilizer driving means formed for vertical reciprocation of said stabilizer means and releasably secured to a vertically reciprocal extension means and to a vertically reciprocable frame portion of said stabilizer means by sleeve means;

releasing said sleeve means from said extension means while maintaining said sleeve means secured to said frame portion, said extension means being mounted for vertical reciprocation in guide means carried by said carriage;

vertically displacing said sleeve means and said frame portion with said stabilizer driving means; securing said frame portion for support of the weight of said stabilizer means to said guide means; releasing said sleeve means from said frame portion while maintaining said frame portion secured to said guide means; vertically displacing said sleeve means with respect to said frame portion with said stabilizer driving means to a selected adjusted position on said frame portion;

locking said sleeve means to said frame portion at said adjusted position; and thereafter locking said extension means to said sleeve means and said frame portion and releasing frame portion from said guide means for reciprocation of said extension means, frame portion and stabilizer by said stabilizer driving means while locked in said adjusted position.

, 7. A method of adjusting the height of a load stabilizer over fork means as defined in claim 6 and the additional steps of:

securing said extension means to said frame portion to effect the securing of said frame portion to the 9 l guide means for support of the weight of said stabimeans from said frame portion and releasing said lizer means, said extension means being formed to frame portion from said guide means; and transfer the weight of said stabilizer means to said vertically displacing said sleeve means and said frame guide means; and portion until said sleeve means is adjacent said exafter locking said sleeve means to said frame portion tension means.

at said adjusted position, releasing said extension 

1. In a forklift truck having an upright lift frame, a movable carriage mounted to said frame for vertical reciprocation, said carriage further being provided with fork means for support of a load, load stabilizer means mounted in vertically spaced and substantially superimposed relation to said fork means for vertical reciprocation thereover, and stabilizer driving means connected to said stabilizer means to raise and lower said stabilizer means through a range of heights with respect to said fork means, the improvement comprising: an adjustable load stabilizer frame mounting said stabilizer means on said carriage for selective adjustment of the range of heights above said fork means through which said stabilizer means can be raised and lowered, said stabilizer frame including:
 1. a reciprocating extension means mounted on said carriage for reciprocation in a vertical direction with respect to said fork means;
 2. a stabilizer frame portion mounted on said extension means for vertical reciprocation with respect to said extension means and to said fork means, said stabilizer means being mounted on said frame portion; and
 3. locking means secured to said stabilizer driving means for movement therewith, said locking means being positioned adjacent said extension means and said frame portion and formed for reciprocation with respect thereto and for selective securement to both said extension means and said frame portion, and said locking means being further formed for securement to one of said extension means and said frame portion for reciprocation of only the secured one thereof by said stabilizer driving means.
 2. a stabilizer frame portion mounted on said extension means for vertical reciprocation with respect to said extension means and to said fork means, said stabilizer means being mounted on said frame portion; and
 2. A forklift truck having an adjustable load stabilizer frame as defined in claim 1 wherein, said carriage is formed with a vertically extending guide means; and said extension means is mounted for reciprocation on said guide means, said guide means, extension means and frame portion being mounted in relatively telescoped relation.
 3. locking means secured to said stabilizer driving means for movement therewith, said locking means being positioned adjacent said extension means and said frame portion and formed for reciprocation with respect thereto and for selective securement to both said extension means and said frame portion, and said locking means being further formed for securement to one of said extension means and said frame portion for reciprocation of only the secured one thereof by said stabilizer driving means.
 3. A forklift truck having an adjustable load stabilizer frame as defined in claim 2 wherein, said frame portion is formed with a plurality of vertically spaced horizontally extending channels therethrough; and said locking means is formed as a sleeve substantially surrounding said extension means and said frame portion and formed with a plurality of vertically spaced horizontally extending channels, and one of said channels of said locking means is further alignable with a horizontally extending channel through an upper end of said extension means, at least a pair of said channels in said frame portion being postionable in relative registration with a pair of channels in said sleeve, and said channel in said extension means capable of being in registration with one of said channels in said sleeve and one of said channels in said frame portion, and said locking means further including at least a pair of pin elements removably mounted to extend into said registered channels in said sleeve, said extension means and said frame portion.
 4. A forklift truck having an adjustable load stabilizer frame as defined in claim 2, and stop means mounted on said extension means and formed to limit the downward reciprocation of said locking means with respect to said extension means and further formed to limit the downward reciprocation of said extension means with respect to said guide means; and wherein, said locking means is formed for releasable securement to said frame portion at a first vertical position thereon, and said extension means is formed for releasable securement to said frame portion at a second vertical position thereon.
 5. A forklift truck having an adjustable load stabilizer frame as defined in claim 1, wherein said carriage includes a pair of laterally spaced, vertically extending, tubular guide elements fixedly secured to said carriage for movement with said fork means; said extension means is formed by a pair of tubular extension members telescopically mounted for vertical reciprocation in said guide elements; said frame portion is formed by a pair of frame members telescopically mounted for vertical reciprocation in said pair of tubular extension members and said frame members have said stabilizer means secured to the upper ends thereof; said stabilizer driving means is formed as a hydraulic piston and cylinder and pump means therefor, and one of said piston and cylinder is secured to said carriage and the remaining of said piston and cylinder is secured to a transverse cross-bar extending between said pairs of telescopically mounted members; and said locking means includes, a pair of sleeves secured to opposite ends of said transverse cross-bar with each sleeve being mounted in sliding engagement around said telescopically mounted members, and locking pin means mounted on each of said sleeves and formed for selective releasable securement to said pair of tubular extension members and for selective releasable securement to said pair of frame members.
 6. A method of adjusting the height of a load stabilizer means over a fork means mounted on a vertically reciprocal carriage on a forklift truck comprising: vertically positioning said stabilizer means to a selected vertical height over said fork means by load stabilizer driving means formed for vertical reciprocation of said stabilizer means and releasably secured to a vertically reciprocal extension means and to a vertically reciprocable frame portion of said stabilizer means by sleeve means; releasing said sleeve means from said extension means while maintaining said sleeve means secured to said frame portion, said extension means being mounted for vertical reciprocation in guide means carried by said carriage; vertically displacing said sleeve means and said frame portion with said stabilizer driving means; securing said frame portion for support of the weight of said stabilizer means to said guide means; releasing said sleeve means from said frame portion while maintaining said frame portion secured to said guide means; vertically displacing said sleeve means with respect to said frame portion with said stabilizer driving means to a selected adjusted position on said frame portion; locking said sleeve means to said frame portion at said adjusted position; and thereafter locking said extension means to said sleeve means and said frame portion and releasing frame portion from said guide means for reciprocation of said extension means, frame portion and stabilizer by said stabilizer driving means while locked in said adjusted position.
 7. A method of adjusting the height of a load stabilizer over fork means as defined in claim 6 and the additional steps of: securing said extension means to said frame portion to effect the securing of said frame portion to the guide means for support of the weight of sAid stabilizer means, said extension means being formed to transfer the weight of said stabilizer means to said guide means; and after locking said sleeve means to said frame portion at said adjusted position, releasing said extension means from said frame portion and releasing said frame portion from said guide means; and vertically displacing said sleeve means and said frame portion until said sleeve means is adjacent said extension means. 